Electromagnetic sound pickup for the reproduction of quadrophonic sound recordings and the like

ABSTRACT

An electromagnetic sound pickup for use in the production of quadrophonic sound recordings and the like includes at least two scanning devices each suited for different frequency ranges. Each scanning device is arranged on a common mounting means which is rotatably supported about its longitudinal axis in a sound pickup housing in such a manner that the pole piece ends associated with each scanning device can selectively be brought into contact with pole piece parts which are fixed with respect to the housing by rotating the mounting means about its longitudinal axis.

States atiet [191 I Unite Kuhn 1 NEW. 2@, M74

[ ELECTROMAGNETIC SOUND PICKUP FOR THE REPRODUCTION OF QUADROPHONICSOUND RECORDINGS AND THE LIKE [75] Inventor: Hans-Robert Kuhn, Kiel,Germany [73] Assignee: Ellectroacustic GmbIlI, Kiel, Germany 22 Filed:Apr. 18,1973 21 Appl. No'.: 352,189

[30] Foreign Application Priority Data June 21, 1972 Germany 2230203[52] US. Cl. 179/1004] K,274/37 [51] Int. Cl I-ll04r 11/12 [58] Field ofSearch l79/l00.4l K, 100.41 C,

l79/l00.41 D, 100.4] M, 100.41 Z, 100.4 ST, 1 GO, 100.1 TD; 274/37 [56]References Cited UNITED STATES PATENTS 3,401,237 8/1968 Takayanagil79/l00.4 ST

5/l97l Obata l79/l00.4l M

3,576,955. 7 3,700,829 10/!972 Anneberg et ul 179/l00.4l Z 3,720,7963/1973 Honma H l79/l0().4l K

Primary Examiner Stuart N. Hec'ker Attorney, Agent, or Firm-Herbert L.Lerner [57] ABSTRACT An electromagnetic sound pickup for use in theproduction of quadrophonic sound recordings and the like includes atleast two scanning devices each suited for different frequency ranges.Each scanning device is arranged on a common mounting means which isrotatably supported about its longitudinal axis in a sound pickuphousing in such a manner that the pole piece ends associated with eachscanning device can selectively be brought into contact with pole pieceparts which are fixed with respect to the housing by rotating themounting means about its longitudinal axis.

7 Claims, 3 Drawing Figures ELECTROMAGNETIC SOUND PICKUP FOR THEREPRODUCTION OF QUADROPHONIC SOUND RECORDINGS AND THE LIKE Thisinvention relates to an electromagnetic sound pick-up, preferably forthe reproduction of quadrophonic sound recordings, in which there areprovided pole pieces each consisting of two separate parts. One of theparts, which carries induction coils, is attached in fixed relation in asound pickup housing, and the other pole piece part or pole piece end isdetachably assembled to the pole piece part which is fixed to the pickuphousing. Located between or in front of each two pairs of pole pieceends is a magnetic armature which is firmly connected with a needlecarrier, the latter being supported so that it can be elasticallydeflected. The armature, armature bearing, and the needle carrier arecombined to define a structural unit forming a scanning device.

Two methods for quadrophonic sound recording have found acceptance. Inone method, the audiofrequency voltages of each of two of the fourchannels are combined according to a matrix method, known per se, forthe purpose of transmission over only two channels. In the other method,the audio-frequency voltages of two channels are additionally modulated,after encoding, onto an auxiliary carrier situated above theaudio-frequency range.

Depending on the recording method used, pickup devices which havedifferent mechanical properties and which are specially suited fordifferent frequency ranges are required for the scanning of the records.In playing back records which have been recorded by these differentmethods, in order to avoid having to each time pull out one scanningdevice from the sound pickup and insert the other, there are provided,according to the present invention, at least two such scanning deviceseach suited for the different frequency ranges wherein the scanningdevices, together with the pole piece ends associated with them, arearranged on a common mounting means which is rotatably supported aboutits longitudinal axis in the sound pickup housing in such a manner that,by rotating the mounting means, thepole piece ends associated with thescanning devices can selectably be brought in contact with the polepiece parts that are fixed with respect to the housing.

It is well known that, in order to obtain sufficient output voltage withelectromagnetic sound pickups, the largest possible number of turns onthe induction coils is necessary. However, with an increasing number ofturns, the inductance of the induction coils also increases. Togetherwith the distributed capacity of the coil and the capacity of the wiringbetween the scanning system and the amplifier, this inductance producesan electric resonance and thereby a magnification of the amplitudes inthe region of the resonance frequency. Eliminating this amplitudemagnification by damping is not feasible because crosstalk is increasedthereby. In known customary pickups presently in use. the inductance ofthe coil is, therefore, given such values that together with the valuesof the capacitances present, an electric resonance above 20 kHz results,that is, above the range of useful frequencies to be transmitted.

In the quadrophonic method with auxiliary carrier, in order that theresulting electric resonance point can also be placed above the usablefrequency range, that is, above the audio-frequency voltages on thecarrier, it is necessary that the induction coils have lower inductancevalues. In a practical embodiment of the present invention, therefore,each of the two induction coils have a tap to which an operator switcheswhen going to the quadrophonic method with auxiliary carrier. The switchfor switching from the one end of the coils to the taps (or vice versa)is coupled with the rotatably supported mounting means. In this mannerassurance is always provided that the inductance matched to thefrequency range to be scanned is switched into the circuit.

, Other features which are considered as characteristies for theinvention are set forth in the appended claims.

Although the invention is illustrated and described in relationship to aspecific embodiment, it is nevertheless not intended to be limited tothe details shown, since various modifications and structural changesmay be made therein without departing from the spirit of the inventionand within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings, in which:

FIG. I is longitudinal cross sectional view taken along the line A-B inFIG. 2 and showing an electro-- magnetic sound pickup system accordingto one embodiment of the invention.

FIG. 2 is a view of the sound pickup system looking along the line C-Din FIG. ll.

FIG. 3 is a view of the switching plate for switching the inductancevalues of the induction coils as used in mature of a mass as small aspossible is, therefore, re-

the sound pickup system shown in FIGS. 1 and 2.

Referring to FIG. 1, there is shown one of two pole piece parts 2 whichare fixed with respect to a pickup housing. FIG. 1 also shows theassociated induction coil 3 which is also disposed inside the pickuphousing 1 along with the pole piece part 2. The induction coil 3 isprovided with a tap (not shown in FIG. 1) which, together with the oneend of the coil winding, is led to contacts 13 and 14 which are arrangedoutside the housing 1. A mounting means 4 is supported for rotationabout its longitudinal axis on the housing 1. The mounting means 4mounts scanning devices 5, 6, 7 (see also FIG. 2) suitable for scanningdifferent frequency ranges with their associated pole piece ends 8, 9,10 (see also FIG. 1). The scanning devices are displaced by 120 relativeto each other. A shaft 11 for the mounting means 4 extends through thepickup housing 1 and carries a switch plate 12 on its backside.

This switch plate 12 is provided on both sides with conductor tracks, ascan be seen in detail in FIG. 3, and is arranged so that the conductorson one side are contacted by the contacts 13 and 14 and the conductorson the other side by contact pins 17 and 18 of the pickup. The contactpins 17 and 18 of the pickup are arranged in a receptacle 16 which isrigidly connected to the pickup housing 1. A knob 20 is provided forrotating the mounting means 4.

The arrangement of the scanning devices 5, 6, 7 with their associatedpole piece ends 8, 9, 10 is shown in FIG. 2. A detent spring 21 isprovided which has one end fastened to the receptacle 16 (FIG. 1) andwhich carries at its free end a conical pin 22. When switching from onescanning device to another, the detent spring 21 snaps with this pin 22into corresponding recesses 23, 24 25, which are provided in themounting means 4.

Simultaneously with the switching of the scanning device suited for thefrequency range to be scanned, which is accomplished by turning a knob20 attached to the mounting means 4, the switch plate 12 is switched tothe inductance values of the induction coils which correspond to thisfrequency range.

FIG. 3 shows conductor tracks 26 and 27 arranged on the switch plate 12with their switch contacts 28, 29, 30 and 31, 32 33, respectively. Alsoshown in FIG. 3 is a second induction coil 34 having a tap leading to acontact 35 and also having one end which leads to a contact 36. Theother end of the coil 34 is connected with the one end of the inductioncoil 3 via a wire 15, and the latter is connected to the pickup contactpin 19. The other end of the coil 3 leads to the contact 13 and its tapto the contact 14. I. For switching to the appropriate inductance valuesof the induction coil 3, the conductor track 26, on the one hand, isassociated with the pickup contact pin 17 which slides continuously onthe conductor track 26 and, on the other hand, makes connection with thecontacts 13 or 14 of the coil 3 via the switch contacts 28, 29 or 30,depending on the position of the switch plate 12.

For switching to the appropriate inductance values of the induction coil34 which is associated with the conductor tract 27', on the one hand,the pickup contact pin 18 slides continuously on the conductor tract 27,and, on the other hand, makes connection with the contacts 35 or 36 ofthe coil 34 via the switch contacts 31, 32 or 33 depending on theposition of the switch plate 12.

What I claim is:

1. An electromagnetic sound pickup for use in the production ofquadrophonic sound recordings and the like comprising a housing, polepieces each having two parts, one of said parts carrying an inductioncoil and being fixedly mounted on said housing, the other of said partsbeing detachably assembled to said one part which is fixed to saidhousing, a magnetic armature associated with each detachably assembledpart of said pole pieces, a needle carrier connected to each saidmagnetic armature, said needle carrier being supported so that it can beelastically deflected, each said magnetic armature and connected needlecarrier defining a structural unit forming a scanning device, at leasttwo scanning devices, each suited for different frequency ranges, acommon mounting means rotatably mounted on said housing, each of saidscanning devices together with its associated part of said pole piecesbeing mounted on said mounting means, whereby rotation of said mountingmeans causes each said other part of said pole pieces to selectively bebrought into contact with the one part of said pole piece that is fixedto said housmg.

2. An electromagnetic sound pickup according to claim 1 including meansfor changing the inductance of said induction coils.

3. An electromagnetic sound pickup according to claim 2 wherein each ofsaid induction coils is provided with at least one tap, each of saidcoils having an end, a switch means for switching between said tap andthe respective coil end, said switch being coupled for rotation withsaid mounting means.

4. An electromagnetic sound pickup according to claim 3 wherein saidswitch means includes a switch plate having conductor tracks, and pickupcontact means in continuous sliding contact with said conductor tracks.

5. An electromagnetic sound pickup according to claim 4 wherein saidswitch means includes a plurality of switch contacts on said switchplate, and further pickup contact means contacting said switch contactsdepending on the rotary position of said switch plate.

ter in the desired rotatable position.

* l l l

1. An electromagnetic sound pickup for use in the production ofquadrophonic sound recordings and the like comprising a housing, polepieces each having two parts, one of said parts carrying an inductioncoil and being fixedly mounted on said housing, the other of said partsbeing detachably assembled to said one part which is fixed to saidhousing, a magnetic armature associated with each detachably assembledpart of said pole pieces, a needle carrier connected to each saidmagnetic armature, said needle carrier being supported so that it can beelastically deflected, each said magnetic armature and connected needlecarrier defining a structural unit forming a scanning device, at leasttwo scanning devices, each suited for different frequency ranges, acommon mounting means rotatably mounted on said housing, each of saidscanning devices together with its associated part of said pole piecesbeing mounted on said mounting means, whereby rotation of said mountingmeans causes each said other part of said pole pieces to selectively bebrought into contact with the one part of said pole piece that is fixedto said housing.
 2. An electromagnetic sound pickup according to claim 1including means for changing the inductance of said induction coils. 3.An electromagnetic sound pickup according to claim 2 wherein eacH ofsaid induction coils is provided with at least one tap, each of saidcoils having an end, a switch means for switching between said tap andthe respective coil end, said switch being coupled for rotation withsaid mounting means.
 4. An electromagnetic sound pickup according toclaim 3 wherein said switch means includes a switch plate havingconductor tracks, and pickup contact means in continuous sliding contactwith said conductor tracks.
 5. An electromagnetic sound pickup accordingto claim 4 wherein said switch means includes a plurality of switchcontacts on said switch plate, and further pickup contact meanscontacting said switch contacts depending on the rotary position of saidswitch plate.
 6. An electromagnetic sound pickup according to claim 1including means adapted to be grasped by an operator to rotate saidmounting means.
 7. An electromagnetic sound pickup according to claim 1including detent means on said housing and operable to engage saidmounting means to secure the latter in the desired rotatable position.